For they could not endure that which was commanded - They could not sustain the awe produced by the fact that God uttered his commands himself. The meaning is not that the commands themselves were intolerable, but that the manner in which they were communicated inspired a terror which they could not bear. They feared that they should die; Exodus 20:19.
And if so much as a beast touch the mountain, it shall be stoned - Exodus 19:13. The prohibition was, that neither beast nor man should touch it on pain of death. The punishment was to be either by stoning, or being "shot through."
Or thrust through with a dart - Exodus 19:13. "Or shot through." This phrase, however, though it is found in the common editions of the New Testament, is wanting in all the more valuable manuscripts; in all the ancient versions; and it occurs in none of the Greek ecclesiastical writers, with one exception. It is omitted now by almost all editors of the New Testament. It is beyond all doubt an addition of later times, taken from the Septuagint of Exodus 19:13. Its omission does not injure the sense.

For they could not endure that which was commanded,.... In the law; not that they disliked and despised the law, as unregenerate men do; but they could not endure it, or bear it, as a yoke, it being a yoke of bondage; nor as a covenant of works, it requiring perfect obedience, but giving no strength to perform; and as it showed them their sins, but did not direct them to a Saviour; as it was an accusing, cursing, and condemning law; and, as a fiery one, revealing wrath, and filling the conscience with it; unless this should have any respect to the following edict, more particularly:
and if so much as a beast touch the mountain, it shall be stoned or thrust through with a dart; and, if a beast, much more a man: and, how easily, through inadvertence, might this be done? and how terrible was the punishment? nothing less than death, by stoning, or being shot: and this they could not bear to hear, or think of: the last clause, "or thrust through with a dart", is wanting in the Alexandrian and Beza's Claromontane copies, in the Vulgate Latin, and all the Oriental versions; and yet is necessary to be retained, being in the original text, in Exodus 19:12.

that which was commanded--"the interdict" [TITTMANN]. A stern interdictory mandate is meant.
And--rather, "Even if a beast (much more a man) touch," &c.
or thrust through with a dart--omitted in the oldest manuscripts. The full interdict in Exodus 19:12-13 is abbreviated here; the beast alone, being put for "whether man or beast"; the stoning, which applies to the human offender, alone being specified, the beast's punishment, namely, the being thrust through with a dart, being left to be understood.

For they could not bear - The terror which seized them, when they heard those words proclaimed, If even a beast, &c. Exodus 19:12, &c.